Handing a deck of cards to Sarah Ludwig, the psychologist said, ''I want you to put the cards in order by suit, but keep in a separate pile those cards with the letter T in their names.'' Sarah, 15, planned her strategy and, as the psychologist clicked a stopwatch, began sorting.

Richard Belmont, an airline pilot, went to the emergency room on Christmas Eve in 1989 for what he thought was a pulled abdominal muscle. It turned out to be non-Hodgkin's lymphoma, a usually incurable cancer. ''I think it's your last Christmas,'' Mr. Belmont recalled being told by the doctor. ...